Influence of Ammonium Sulfate, Imazapyr, Temperature, and Relative Humidity on the Absorption and Translocation of Imazethapyr

The effects of 1.24 kg ha −1 ammonium sulfate, 5 g ae ha −1 of the isopropylamine salt of imazapyr, and air temperatures of 18, 27, or 35 C at 40 or 100% relative humidity (RH) on the absorption and translocation of the ammonium salt of 14 C-imazethapyr applied postemergence to pitted morningglory were evaluated. Absorption of 14 C-imazethapyr was greater at 100 than at 40% RH (88 vs. 47%). At 40% RH, absorption was increased to 79% by the addition of ammonium sulfate. At 100% RH absorption was similar with all treatments. Translocation of 14 C-imazethapyr applied alone was greater at 100 than at 40% RH (34 vs. 17%). Addition of ammonium sulfate increased translocation at 40% RH but not at 100%. Addition of imazapyr did not affect 14 C translocation. Distribution of 14 C throughout the plant was more acropetal than basipetal with the greatest distribution at 35 C.